Local energy balance, specific heats and the Oberbeck-Boussinesq approximation

A thermodynamic argument is proposed in order to discuss the most appropriate form of the local energy balance equation within the Oberbeck-Boussinesq approximation. The study is devoted to establish the correct thermodynamic property to be used in order to express the relationship between the change of internal energy and the temperature change. It is noted that, if the fluid is a perfect gas, this property must be identified with the specific heat at constant volume. If the fluid is a liquid, a definitely reliable approximation identifies this thermodynamic property with the specific heat at constant pressure. No explicit pressure work term must be present in the energy balance. The reasoning is extended to the case of fluid saturated porous media.Comment: 14 pages, 2 figures, 1 table, submitted for publicatio

The first occurrence of the Ponto-Caspian invader, Hemimysis anomala G.O. sars, 1907 (Mysidacea) in the UK

An invasive Ponto-Caspian mysid, Hemimysis anomala G.O. Sars, 1907, was recorded in England for the first time in 2004. Usually a deep water species, in England H. anomala has been observed in shallow waters, in which it shelters under or within anthropogenic structures during daylight. This behaviour renders traditional, net-based survey methods ineffective. Therefore, a distribution survey of the English East Midlands was conducted by searching for individuals by torchlight after dark. H. anomala was found to be widespread within the study area, occurring at 24 out of 51 sites surveyed. However, the geographical limits of its distribution were not determined. The species occurred at low densities in canals and in backwaters of the River Trent, whilst dense swarms were observed in September 2005 in a regatta lake connected to the River Trent. H. anomala has the potential to spread through England's canal network and could colonize the lower reaches and estuaries of rivers including the River Thames and River Severn. Habitat preference analysis indicated that flowing water and absence of shelter prevented population establishment, although the species' U.K. distribution suggests that it can migrate through such areas of unsuitable habitat

Heatline visualization of natural convection in a porous cavity occupied by a fluid with temperature-dependent viscosity

Temperature dependent viscosity effect in buoyancy driven flow, of a gas or a liquid, in an enclosure filled with a porous medium is studied numerically, based on the general model of momentum transfer in a porous medium. The Arrhenius model, which proposes an exponential form of viscosity-temperature relation, is applied to examine three cases of viscosity-temperature relation: constant, decreasing and increasing. Application of arithmetic and harmonic mean values of the viscosity is also investigated for their ability to represent the Nusselt number versus the effective Rayleigh number. Heatlines are illustrated for a more comprehensive investigation of the problem

Enhancing graduate employability in hospitality, leisure, sport and tourism

This paper is work-in-progress. The purpose of the paper is to describe the aims, context and methodology of a recently approved Fund for the Development of Teaching and Learning (FDTL) Phase 5 project. The aim of the project is to develop, implement and evaluate a range of curriculum interventions to enhance the employability of Hospitality, Leisure, Sport and Tourism (HLST) student

Roll convection of binary fluid mixtures in porous media

We investigate theoretically the nonlinear state of ideal straight rolls in the Rayleigh-B\'enard system of a fluid layer heated from below with a porous medium using a Galerkin method. Applying the Oberbeck-Boussinesq approximation, binary mixtures with positive separation ratio are studied and compared to one-component fluids. Our results for the structural properties of roll convection resemble qualitatively the situation in the Rayleigh--B\'enard system without porous medium except for the fact that the streamlines of binary mixtures are deformed in the so-called Soret regime. The deformation of the streamlines is explained by means of the Darcy equation which is used to describe the transport of momentum. In addition to the properties of the rolls, their stability against arbitrary infinitesimal perturbations is investigated. We compute stability balloons for the pure fluid case as well as for a wide parameter range of Lewis numbers and separation ratios which are typical for binary gas and fluid mixtures. The stability regions of rolls are found to be restricted by a crossroll, a zigzag and a new type of oscillatory instability mechanism, which can be related to the crossroll mechanism

Effects of viscous dissipation and boundary conditions on forced convection in a channel occupied by a saturated porous medium

Forced convection with viscous dissipation in a parallel plate channel filled by a saturated porous medium is investigated numerically. Three different viscous dissipation models are examined. Two different sets of wall conditions are considered: isothermal and isoflux. Analytical expressions are also presented for the asymptotic temperature profile and the asymptotic Nusselt number. With isothermal walls, the Brinkman number significantly influences the developing Nusselt number but not the asymptotic one. At constant wall heat flux, both the developing and the asymptotic Nusselt numbers are affected by the value of the Brinkman number. The Nusselt number is sensitive to the porous medium shape factor under all conditions considered